Definition df-id 4440

Description: Define the identity relation. Definition 9.15 of [Quine] p. 64. For example, 5 _I 5 and -. 4 _I 5. (Contributed by NM, 13-Aug-1995.)

Assertion

Ref	Expression
df-id	|- _I = { <. x , y >. | x = y }

Distinct variable group:   x, y

Detailed syntax breakdown of Definition df-id

Step	Hyp	Ref	Expression
1		cid 4435	. 2 class _I
2		vx	. . . 4 setvar x
3		vy	. . . 4 setvar y
4	2, 3	weq 1556	. . 3 wff x = y
5	4, 2, 3	copab 4192	. 2 class { <. x , y >. | x = y }
6	1, 5	wceq 1402	1 wff _I = { <. x , y >. | x = y }

This definition is used by:  reli  4911  ideqg  4933  opabresid  5119  cnvi  5195  dffun2  5390  ider  6844  cnmptid  15507